Quote:
Originally Posted by ZDan
You have to include driver weight! Totally stock power/weight with half a tank of fuel is ~14.2:1 with 165 lb. driver. Lose 120 lb. and it's 13.6 lb/hp. 4% - 5% difference.
I have trouble detecting 10% at seat-of-pants, but for sure a stopwatch would notice 5% given a consistent driver and conditions.
Drag = 1/2 rho v^2 cD A. In awkward 'murican units, drag at 100mph in lb = 1/2 * (0.00237 sl/ft^3) * (146.7 ft/s)^2 * 0.29 * 20ft^2
0.29 cD, 20 ft^2 frontal area, aero drag at 100mph is 147.9 lb.
For 0.27 cD, 137.7 lb.
10.2 lb. difference in aero drag.
The horsepower freed up by reducing drag by 10.2 lb. at 100mph (146.7 ft/s) is:
hp = (10.2 lb)*(146.7 ft/s) / [(550 ft-lb/s) / hp] = 2.72 hp
Around +1.6% vs. rwhp available.
Maybe, maybe not... IMO there really isn't a lot of "low-hanging fruit" to reduce aero drag on a car that's already very slippery from the factory. Pretty much all that's easy to get has been got...
Weight reduction maybe, aero drag reduction, I still don't think you're going to find anything meaningful there.
I do appreciate the idea of doing a little here, little there, *everywhere* to get a cumulative benefit! But for me, due to laziness and being right at the weight limit for my class anyway, I just drive the car to the track and run it, pretty much... My only mods are lowering springs and camber plates and tires, but those mods are worth *seconds* per lap! Hard to get enthusiastic about spending more time and $$$ for *maybe* a tenth or two...
If I had a lot more time and tools and garage and storage space (and skill), I'd be a lot more interested in doing mods for small benefits, or even just for the f of it!
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Curb weight is with full tank gas included. But I guess driver weight should be added. Also I did with 230hp crank as most people have header back + tune befor looking for more “speed” performance.
I guess I over remembered the benefit of lowering cd.
I have a garage/tools, and do all my own mods for fun as a hobby and have draggy to see before and after improvements at various acceleration points. I knew each weight + drag mod alone wouldn’t make a huge seat of pants difference going in so I did battery, trunk junk, cf driveshaft, jdm underpanels, trans tunnel covers, underdrive accessory pulleys, and fluidampr crank pulley all at same time. The accumulated effect was pretty noticeable. Probably half as noticeable seat of pants wise as my ace header + custom e-tune was.